Definition(s) of PERFORMANCEHow is TECHNICAL SPEED being used - Where did we lost CYCLES?
A machine should be available to run reliably at a given speed.
When it is NOT running its theoretical maximum speed:
When and Why was it NOT maximal?
Was the machine running at maximum speed or not?
What Unit of Measure to use?
- maximum speed is 10 seconds per product
- maximum speed is 6 products per minute
Nevertheless since OEE is primarily a shopfloor tool, and people on the shopfloor usually rather talk about ‘units being produced’ than ‘seconds it has taken to produce a unit’, it is preferred to register speed in units, not in time.
The parameters for Performance
can be expressed in either TIME or QUANTITY,
- TIME is needed for correct calculations
- QUANTITY is preferred for effective communication
The different kinds of Maximum Speed of a machine
Name Plate Capacity
The correct use of NPC
The NPC should not be taken granted for. More than once it was discovered to include all kind of hidden losses.
The manufacturer might have chosen a low NPC for reasons of liability or to ‘fit’ the equipment with other equipment in a line.
Usually the supplier defines the NPC using a “standard product”.
To what extent this standard product is similar to your own product must be investigated.
Maximum Speed of a Product on a Machine
- the theoretical maximum speed for A is 500kg/250gram= 2000 pcs per hour.
- The theoretical maximum speed for B is 500kg/500gram= 1000 pcs per hour.
The theoretical maximum speed for a product-machine combination is called ‘The Standard’.
This means that each product group on a certain machine can have its own maximum speed.
Attention: proceed here almost mathematically! A beaker of 250 ml theoretically takes half as long to feel as a beaker of 500 ml.
250 ml strawberry yogurt and 250 ml plum yogurt should therefore have the same maximum speed on a certain system.
If the plum yoghurt is driven more slowly, the maximum speed should not be reduced, but rather be investigated what is slowing down the plum yoghurt!
The Standard is specifically not called ‘Norm’, since this word has negative associations related to agreed wages for many people in different countries.
How ‘Maximal’ is Maximum Speed?
'Maximal' means: It can IMPOSSIBLY be more...
This statement should be taken serious. If not done so, situations may (and do) occur where the shopfloor is filled with scrap, the machine is suffering one breakdown after the other and still accounts for 80% or more OEE. How?
70% Availability, 80 % Quality, 143% Performance = 80% OEE !
As soon as the performance rate goes over 100% (indicating the standard is chosen too low!) the beautiful balance of the OEE parameters is broken, and the focus may be taken away from what it is all about: identifying and reducing losses.
In cases where the maximum speed has to be determined based upon a Best Of Best analysis, it should be considered that this BOB is achieved under the former and current circumstances, including current losses.
Since in the end even standards are broken by product- and equipment improvement, the BOB should not be considered too easily as maximum value. As a rule of thumb the BOB value should be raised with at least 10 to 25% to serve as Standard.
The standard is the theoretical maximum speed for a product(group) on the machine;
thus the performance rate never exceeds 100%
The theoretical maximum capacity of the equipment
And thus it can NEVER be more, so:
At well-chosen Standards, the performance rate will NEVER exceed 100%,
unless the product or the machine fundamentally changes
The goal of OEE is NOT to be close to 100% or to be high at all!
The aim is to have a fixed reference point on the system over the years
in order to be able to see if (and where) you improve.
A low OEE at the beginning is good!
There is a lot of potential for improvement!
Speed of a product-mix
Performance of multiple products with different speeds
In cases where multiple products have been produced (both sequentially
as well as parallel) the performance (as well as the quality) part of the OEE is calculated as a weighted average; calculated between several expected output ranges.
Definitions Speed Losses
What determines 'Speed Losses' in Performance Rate?
Performance rate reveals two losses: Reduced Speed and Minor Stops
The difference between the theoretical maximum speed and the actual speed is the speed-loss. However this speed loss can be divided into two categories:
1. Reduced Speed Loss
Those are the losses arising from deliberately running the machine at a lower speed (the Set Speed): It is the difference between the set speed and the theoretically possible maximum speed. To be called: Reduced Speed Loss.
2. Minor Stops
Losses arising from speed-fluctuations (and ‘short idling’) between the Actual Speed and the Set Speed. Such fluctuations do not need to be individually identified and are called: Minor Stops.
How do Actual, Set and Maximum Speed relate
1. Actual Speed
Actual speed is calculated by dividing the actually produced output (regardless its quality) by the time it took to produce it.
60 items produced in 10 minutes means a speed of 6 items per minute.
2. Set Speed
Typically, a machine running a certain product is set to a lower speed than theoretically possible. This is the SET SPEED. When running 10 minutes on a set speed of 6, we expect 60 products to be produced. However, when after 10 minutes actually only 58 product are counted, this means 2 product are ‘lost’ due to small speed fluctuations or even real mini-stops: ‘Minor Stops’.
Actual Speed can NEVER be higher than Set Speed
Whenever this might occur, this indicates the need of a calibration of the Set Speed gauge or the output counter!
3. Maximum Speed
Since the maximum speed is defined as the theoretical maximum speed of a product on a machine, the actual speed NOR set speed can EVER be higher.
Actual Speed can NEVER be higher than Maximum Speed
Set Speed can NEVER be higher than Maximum Speed
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